1. Field of the Invention
The present invention relates to a liquid discharge head that discharges ink toward a recording medium such as recording paper and a method of making the liquid discharge head.
2. Description of the Related Art
A liquid discharge head includes a recording element substrate, a flexible wiring substrate, and a support member. Electrothermal transducers, ink chambers, and other components are disposed in the recording element substrate. The flexible wiring substrate electrically connects the recording element substrate to a recording apparatus body. The support member supports the recording element substrate and the flexible wiring substrate. In general, the recording element substrate and the flexible wiring substrate are affixed to and supported by the support member. Electrode lead wires, which extend from the flexible wiring substrate, are superposed on and joined to electrode pads of the recording element substrate. The electrode lead wires, the electrode pads, and the joints therebetween are sealed with a sealant.
In an existing technology, the front side of the electrode lead wires and the back side of the electrode lead wires are sealed with different sealants. To be specific, the recording element substrate is disposed in a recess of the support member, and a gap between an inner surface of the recess and a side surface of the recording element substrate is filled with a first sealant. The first sealant has a comparatively high fluidity and can flow into a small gap on the back side of the electrode lead wires, while the first sealant has elasticity when cured. The back side of the electrode lead wire is sealed with the first sealant having such characteristics. Moreover, a second sealant is applied to the front side of the electrode lead wires including the joints between the electrode lead wires are the electrode pads. The second sealant has high adhesion strength and hardness when cured and is capable of maintaining the shape with which the sealant was applied. The second sealant protects the electrode lead wires, the electrode pads, and the joints against an external force that is exerted on these portions due to wiping or the like. In the description below, the electrode lead wires, the electrode pads, and the joints may be collectively referred to as an “electrical connection portion”.
It is desirable that a sealant is not in contact with the outer periphery of the recording element substrate excluding the electrical connection portion. In other words, it is desirable that the sealant be applied to only a predetermined region of the outer periphery of the recording element substrate. This is because, an unwanted external force may act on the recording element substrate when the sealant expands and contracts due to change in the environment. In particular, if the size of the recording element substrate is reduced in order to reduce the size of the liquid discharge head, it becomes more likely that the recording element substrate become deformed by such an external force, and thereby ink discharge error may occur or the landing accuracy of ink droplets may decrease.
If a sealant having a high fluidity, such as the aforementioned first sealant, is used to seal the electrical connection portion, the sealant may flow out of the predetermined region. On the other hand, if a sealant having a high viscosity, such as the aforementioned second sealant, is used to seal the electrical connection portion, the electrical connection portion may not be completely covered by the sealant.
U.S. Pat. No. 7,240,991 describes a method of forming a barrier of an adhesive to prevent a sealant having a high fluidity from flowing out of a predetermined region. To be specific, a barrier is formed between a region of the outer periphery of a recording element substrate in which an electrical connection portion is formed and the remaining region so as to separate the region from the remaining region. After forming the barrier, the sealant is applied.
With the technology described in U.S. Pat. No. 7,240,991, the number of used materials increases because the barrier is formed from an adhesive that is different from the sealant. Moreover, because the steps of applying the adhesive and curing the adhesive are necessary, the number of production steps increase and thereby the production cost may increase.